Professor John Ashton said a four-day week could help ease mental and physical health problems. Photograph: Souvid Datta for the Guardian

One of Britain's leading doctors has called for the country to switch to a four-day week to help combat high levels of work-related stress, let people spend more time with their families or exercising, and reduce unemployment.

Bringing the standard working week down from five to four days would also help address medical conditions, such as high blood pressure and the mental ill-health associated with overwork or lack of work, Prof John Ashton said.

The president of the UK Faculty of Public Health said the five-day week should be phased out to end what he called "a maldistribution of work" that is damaging many people's health.

"When you look at the way we lead our lives, the stress that people are under, the pressure on time and sickness absence, [work-related] mental health is clearly a major issue. We should be moving towards a four-day week because the problem we have in the world of work is you've got a proportion of the population who are working too hard and a proportion that haven't got jobs", Ashton said.

"We've got a maldistribution of work. The lunch-hour has gone; people just have a sandwich at their desk and carry on working," added the leader of the UK's 3,300 public-health experts working in the NHS, local government and academia.

The Faculty of Public Health's members work on issues such as obesity, poor diet, alcohol misuse and smoking, often related to poverty, unemployment or poor housing, and also to try to narrow widening health inequalities between the rich and poor. Ashton is using his three-year presidency of the organisation to raise awareness of the fact that mental health problems, such as anxiety and depression, can be either a cause or effect of many public health issues.

"We need a four-day week so that people can enjoy their lives, have more time with their families, and maybe reduce high blood pressure because people might start exercising on that extra day.

"If you've got two people in a couple working, they need to be able to work in such a way that they can spend time together with their children. It's a nightmare," said Ashton, who worked in the NHS for 42 years until he retired last year.

He cited the example of a four-day week giving parents the time to collect their children from school.

Britons work some of the longest hours in Europe, which surveys have linked to stress, sleep problems, reduced productivity and the taking of sick leave.

"My concern is that too many people are working too long hours and too hard, and too many people aren't working at all. A large number of people are working crazy hours and a significant amount of people can't get work," Ashton said.

A YouGov survey in April found that 57% of workers support the idea of a four-day week, and that 71% think it would make Britain a happier place.

"It would mean that people might smile more and be happier, and improve general health," Ashton said.

Employees struggling to cope with working too much can end up stressed or with high blood pressure or problems in their relationship, and even resort to alcohol or drugs, he said.

"It [a four-day week] is viable. We need an ambition in the next 10 to 20 years to move to that on a European level. We've had the European working-time directive. Why couldn't we have the ambition to move to a four-day week? The fifth day could be a community activity day, a giving back day. This is how you operationalise the big society," he said.

The Trades Union Congress said many workers would welcome moving to a four-day week.

"Too few people in the UK are able to work the hours they want and need. Far too many still work part-time when they want a full-time job, leaving them struggling to make ends meet," said Frances O'Grady, the TUC general secretary.

"But there's also a growing problem with excessive working hours, with millions of employees under real pressure as they attempt to balance work with their everyday lives. And despite this week's change in the law it's still too easy for employers to block flexible working requests, however nicely a worker asks.

"A four-day week won't work for everyone, but at the moment it's way beyond the grasp of many who would like to change the hours they work. The new right to request flexible working should be strengthened so that those who need shorter hours have a better chance of getting it."